Binocular treatment for amblyopia: A meta-analysis of randomized clinical trials.

BACKGROUND: To date, there is still no consensus regarding the effect of binocular treatment for amblyopia. The purpose of this systematic review and meta-analysis was to summarize the available evidence to determine whether binocular treatment is more effective than patching in children with amblyopia. METHODS: Four electronic databases (PubMed, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials) were searched for studies that compared binocular treatment and patching in children with amblyopia. The outcome measures were visual acuity and stereopsis. Pooled effects sizes were calculated with a random-effect model. The standardized difference in means (SDM) with 95% confidence intervals (CI) was calculated. Sensitivity analysis and assessment of publication bias were performed. RESULTS: Five randomized clinical trials were included. No significant difference in visual acuity between patients treated with binocular treatment and patching was observed (SDM = -0.12; 95% CI: -0.45-0.20; P = 0.464). No significant difference in stereopsis between patients treated with binocular treatment and patching was observed (SDM = -0.07; 95% CI: -0.61-0.48; P = 0.809). For both variables, the between-study heterogeneity was high (respectively, I2 = 61% and I2 = 57%). CONCLUSIONS: This meta-analysis found no convincing evidence supporting the efficacy of binocular treatment as an alternative to conventional patching. Therefore, the binocular treatment cannot fully replace traditional treatment but, to date, it can be considered a valid complementary therapy in peculiar cases. Further studies are required to determine whether more engaging therapies and new treatment protocols are more effective.

Vision training with VEP biofeedback in amblyopia after the critical period.

PURPOSE: The purpose of this study was to investigate the benefits of vision training with visual evoked potentials (VEP) biofeedback in amblyopia after the critical period in 8 to 17-year (11.5 ± 3.1) old children. METHODS: Ten participants with monocular amblyopia after the critical period underwent a 10-week, 20-session vision training program with the Retimax Vision Trainer device. During each session, the participants were instructed to be as focused as possible onto the fixation point in the middle of the screen. The size of the fixation point and the pitch of the background sound were changing according to VEP parameters and thus provided the participants real-time feedback of their visual performance. RESULTS: The mean BCVA improvement across our group was 0.12 LogMAR (p < 0.01). There was also a significant increase in contrast sensitivity to the FACT chart across all spatial frequencies (all p < 0.05). Electrophysiologic data revealed higher steady-state visual evoked potentials (SS-VEP) amplitudes and correspondingly lower fixation point values in the last 2 weeks of training compared to the first 2 weeks (both p < 0.01). Due to unexplainably low VEP amplitude levels in later trainings compared to those in the beginning in two participants, we have not found a significant correlation between the increase in BCVA and the increase in SS-VEP amplitude (p = 0.88). At the follow-up at 2 and 12 months following the end of training, both BCVA and contrast sensitivity remained within the levels achieved at the end of training. In some participants, however, no improvement of BCVA was observed. CONCLUSIONS: The tested vision training approach demonstrates modest but stable improvement of psychophysical parameters as well as objective characteristics in amblyopia after the critical period. Real-time SS-VEP can be used as an objective parameter to monitor participants' attention during vision training stimulation.

Long-term Monocular Deprivation during Juvenile Critical Period Disrupts Binocular Integration in Mouse Visual Thalamus.

Study of the neural deficits caused by mismatched binocular vision in early childhood has predominantly focused on circuits in the primary visual cortex (V1). Recent evidence has revealed that neurons in mouse dorsolateral geniculate nucleus (dLGN) can undergo rapid ocular dominance plasticity following monocular deprivation (MD). It remains unclear, however, whether the long-lasting deficits attributed to MD during the critical period originate in the thalamus. Using in vivo two-photon Ca2+ imaging of dLGN afferents in superficial layers of V1 in female and male mice, we demonstrate that 14 d MD during the critical period leads to a chronic loss of binocular dLGN inputs while sparing response strength and spatial acuity. Importantly, MD leads to profoundly mismatched visual tuning properties in remaining binocular dLGN afferents. Furthermore, MD impairs binocular modulation, reducing facilitation of responses of both binocular and monocular dLGN inputs during binocular viewing. As predicted by our findings in thalamic inputs, Ca2+ imaging from V1 neurons revealed spared spatial acuity but impaired binocularity in L4 neurons. V1 L2/3 neurons in contrast displayed deficits in both binocularity and spatial acuity. Our data demonstrate that critical-period MD produces long-lasting disruptions in binocular integration beginning in early binocular circuits in dLGN, whereas spatial acuity deficits first arise from circuits further downstream in V1. Our findings indicate that the development of normal binocular vision and spatial acuity depend upon experience-dependent refinement of distinct stages in the mammalian visual system.SIGNIFICANCE STATEMENT Abnormal binocular vision and reduced acuity are hallmarks of amblyopia, a disorder that affects 2%-5% of the population. It is widely thought that the neural deficits underlying amblyopia begin in the circuits of primary visual cortex. Using in vivo two-photon calcium imaging of thalamocortical axons in mice, we show that depriving one eye of input during a critical period in development chronically impairs binocular integration in thalamic inputs to primary visual cortex. In contrast, visual acuity is spared in thalamic inputs. These findings shed new light on the role for developmental mechanisms in the thalamus in establishing binocular vision and may have critical implications for amblyopia.

17α Estradiol promotes plasticity of spared inputs in the adult amblyopic visual cortex.

The promotion of structural and functional plasticity by estrogens is a promising approach to enhance central nervous system function in the aged. However, how the sensitivity to estrogens is regulated across brain regions, age and experience is poorly understood. To ask if estradiol treatment impacts structural and functional plasticity in sensory cortices, we examined the acute effect of 17α-Estradiol in adult Long Evans rats following chronic monocular deprivation, a manipulation that reduces the strength and selectivity of deprived eye vision. Chronic monocular deprivation decreased thalamic input from the deprived eye to the binocular visual cortex and accelerated short-term depression of the deprived eye pathway, but did not change the density of excitatory synapses in primary visual cortex. Importantly, we found that the classical estrogen receptors ERα and ERß were robustly expressed in the adult visual cortex, and that a single dose of 17α-Estradiol reduced the expression of the calcium-binding protein parvalbumin, decreased the integrity of the extracellular matrix and increased the size of excitatory postsynaptic densities. Furthermore, 17α-Estradiol enhanced experience-dependent plasticity in the amblyopic visual cortex, by promoting response potentiation of the pathway served by the non-deprived eye. The promotion of plasticity at synapses serving the non-deprived eye may reflect selectivity for synapses with an initially low probability of neurotransmitter release, and may inform strategies to remap spared inputs around a scotoma or a cortical infarct.

Simplified updates on the pathophysiology and recent developments in the treatment of amblyopia: A review.

Amblyopia is the most common cause of monocular visual impairment affecting 2-5% of the general population. Amblyopia is a developmental cortical disorder of the visual pathway essentially due to abnormal visual stimulus, reaching the binocular cortical cells, which may be multivariate. Ganglion cells are of two types: parvocellular (P cells) and magnocellular (M cells); they are the first step where the light energy is converted in to neural impulse. P cells are involved in fine visual acuity, fine stereopsis, and color vision and M cells are involved in gross stereopsis and movement recognition. Strabismus, refractive error, cataract, and ptosis, occurring during critical period are highly amblyogenic. The critical period extends from birth to 7--8 years. The earlier the clinically significant refractive error and strabismus are detected and treated, the greater the likelihood of preventing amblyopia. Treatment for amblyopia in children includes: optical correction of significant refractive errors, patching, pharmacological treatment, and alternative therapies which include: vision therapy, binocular therapy, and liquid crystal display eyeglasses are newer treatment modalities for amblyopia. Age of starting the treatment is not predictive of outcome, instituting treatment on detection and early detection plays a role in achieving better outcomes. This review aims to give a simplified update on amblyopia, which will be of use to a clinician, in understanding the pathophysiology of the complex condition. We also share the cortical aspects of amblyopia and give recent developments in the treatment of amblyopia.

Amblyopia Affects the ON Visual Pathway More than the OFF.

Visual information reaches the cerebral cortex through parallel ON and OFF pathways that signal the presence of light and dark stimuli in visual scenes. We have previously demonstrated that optical blur reduces visual salience more for light than dark stimuli because it removes the high spatial frequencies from the stimulus, and low spatial frequencies drive weaker ON than OFF cortical responses. Therefore, we hypothesized that sustained optical blur during brain development should weaken ON cortical pathways more than OFF, increasing the dominance of darks in visual perception. Here we provide support for this hypothesis in humans with anisometropic amblyopia who suffered sustained optical blur early after birth in one of the eyes. In addition, we show that the dark dominance in visual perception also increases in strabismic amblyopes that have their vision to high spatial frequencies reduced by mechanisms not associated with optical blur. Together, we show that amblyopia increases visual dark dominance by 3-10 times and that the increase in dark dominance is strongly correlated with amblyopia severity. These results can be replicated with a computational model that uses greater luminance/response saturation in ON than OFF pathways and, as a consequence, reduces more ON than OFF cortical responses to stimuli with low spatial frequencies. We conclude that amblyopia affects the ON cortical pathway more than the OFF, a finding that could have implications for future amblyopia treatments.SIGNIFICANCE STATEMENT Amblyopia is a loss of vision that affects 2-5% of children across the world and originates from a deficit in visual cortical circuitry. Current models assume that amblyopia affects similarly ON and OFF visual pathways, which signal light and dark features in visual scenes. Against this current belief, here we demonstrate that amblyopia affects the ON visual pathway more than the OFF, a finding that could have implications for new amblyopia treatments targeted at strengthening a weak ON visual pathway.

Impaired Spatial Hearing in Amblyopia: Evidence for Calibration of Auditory Maps by Retinocollicular Input in Humans.

Purpose: Evidence from animals and blind humans suggests that early visual experience influences the developmental calibration of auditory localization. Hypothesizing that unilateral amblyopia may involve cross-modal deficits in spatial hearing, we measured the precision and accuracy of sound localization in humans with amblyopia. Methods: All participants passed a standard hearing test. Experiment 1 measured sound localization precision for click stimuli in 10 adults with amblyopia and 10 controls using a minimum audible angle (MAA) task. Experiment 2 measured sound localization error (i.e., accuracy) for click train stimuli in 14 adults with amblyopia and 16 controls using an absolute sound localization task. Results: In Experiment 1, the MAA (mean ± SEM) was significantly greater in the amblyopia group compared with controls (2.75 ± 0.30° vs. 1.69 ± 0.09°, P = 0.006). In Experiment 2, the overall sound localization error was significantly greater in the amblyopia group compared with controls (P = 0.047). The amblyopia group also showed significantly greater sound localization error in the auditory hemispace ipsilateral to the amblyopic eye (P = 0.036). At a location within this auditory hemispace, the magnitude of sound localization error correlated significantly with deficits in stereo acuity (P = 0.036). Conclusions: The precision and accuracy of sound localization are impaired in unilateral amblyopia. The asymmetric pattern of sound localization error suggests that amblyopic vision may interfere with the development of spatial hearing via the retinocollicular pathway.

New advances in amblyopia therapy I: binocular therapies and pharmacologic augmentation.

Amblyopia therapy options have traditionally been limited to penalisation of the non-amblyopic eye with either patching or pharmaceutical penalisation. Solid evidence, mostly from the Pediatric Eye Disease Investigator Group, has validated both number of hours a day of patching and days per week of atropine use. The use of glasses alone has also been established as a good first-line therapy for both anisometropic and strabismic amblyopia. Unfortunately, visual acuity equalisation or even improvement is not always attainable with these methods. Additionally, non-compliance with prescribed therapies contributes to treatment failures, with data supporting difficulty adhering to full treatment sessions. Interest in alternative therapies for amblyopia treatment has long been a topic of interest among researchers and clinicians alike. Incorporating new technology with an understanding of the biological basis of amblyopia has led to enthusiasm for binocular treatment of amblyopia. Early work on perceptual learning as well as more recent enthusiasm for iPad-based dichoptic training have each generated interesting and promising data for vision improvement in amblyopes. Use of pharmaceutical augmentation of traditional therapies has also been investigated. Several different drugs with unique mechanisms of action are thought to be able to neurosensitise the brain and enhance responsiveness to amblyopia therapy. No new treatment has emerged from currently available evidence as superior to the traditional therapies in common practice today. But ongoing investigation into the use of both new technology and the understanding of the neural basis of amblyopia promises alternate or perhaps better cures in the future.

Temporal Ventriloquism Reveals Intact Audiovisual Temporal Integration in Amblyopia.

Purpose: We have shown previously that amblyopia involves impaired detection of asynchrony between auditory and visual events. To distinguish whether this impairment represents a defect in temporal integration or nonintegrative multisensory processing (e.g., cross-modal matching), we used the temporal ventriloquism effect in which visual temporal order judgment (TOJ) is normally enhanced by a lagging auditory click. Methods: Participants with amblyopia (n = 9) and normally sighted controls (n = 9) performed a visual TOJ task. Pairs of clicks accompanied the two lights such that the first click preceded the first light, or second click lagged the second light by 100, 200, or 450 ms. Baseline audiovisual synchrony and visual-only conditions also were tested. Results: Within both groups, just noticeable differences for the visual TOJ task were significantly reduced compared with baseline in the 100- and 200-ms click lag conditions. Within the amblyopia group, poorer stereo acuity and poorer visual acuity in the amblyopic eye were significantly associated with greater enhancement in visual TOJ performance in the 200-ms click lag condition. Conclusions: Audiovisual temporal integration is intact in amblyopia, as indicated by perceptual enhancement in the temporal ventriloquism effect. Furthermore, poorer stereo acuity and poorer visual acuity in the amblyopic eye are associated with a widened temporal binding window for the effect. These findings suggest that previously reported abnormalities in audiovisual multisensory processing may result from impaired cross-modal matching rather than a diminished capacity for temporal audiovisual integration.

[Intervention of acupuncture on abnormal spatiotemporal pattern of visual cortex area 17 neuron in monocular deprivation amblyopia rats].

OBJECTIVE: To preliminarily explore the electrophysiological mechanism of acupuncture on plasticity variability of visual cortex. METHODS: Fifty 14-day-old Wistar rats were randomly divided into a blank group, a model group, an early-stage acupuncture group, a middle-stage acupuncture group and a late-stage acupuncture group, 10 rats in each one. Except the blank group, the rats in the remaining groups were treated with eyelid suture to establish the model of monocular deprivation amblyopia. After model establishment, the rats in the blank group and model group were grasped without any intervention everyday. The rats in the acupuncture groups were treated with acupuncture at bilateral "Jingming" (BL 1), "Cuanzhu" (BL 2), "Fengchi" (GB 20) and "Guangming" (GB 37) on the 3rd, 12th and 21st days into model establishment. The needles were retained for 10 min, once a day for totally 9 days. After treatment, the M-NEMEA technology was applied to measure the discharge amplitude and power spectral density of visual cortex area 17 neuron of each group. RESULTS: Compared with the blank group, the number of discharged neuron of visual cortex area 17 was reduced, and the amplitude was significantly reduced in the model group (both P<0.05). Compared with the model group, the numbers of discharged neuron were increased, and the amplitudes were significantly increased in the early-stage acupuncture group and middle-stage acupuncture group (all P<0.05). The neuron discharge amplitude in the early-stage acupuncture group was higher than those in the middle-stage acupuncture group and late-stage acupuncture group (both P<0.05); the neuron discharge amplitude in the middle-stage acupuncture group was higher than that in the late-stage acupuncture group (P<0.05). In the 120-second time domain of acquisition, the distribution of power spectral density in the blank group was mainly between -105 dB and -100 dB; compared with the blank group, the power spectral density in the model group was increased and distributed between -132 dB and -124 dB; compared with the model group, the power spectral densities in the acupuncture groups was reduced and distributed between -115 dB and -110 dB in the early-stage acupuncture group, -120 dB and -115 dB in the middle-stage acupuncture group and -129 dB and -122 dB in the late-stage acupuncture group. CONCLUSIONS: There are abnormal changes of spatiotemporal pattern in visual cortex area 17 of monocular deprivation rats, but acupuncture can regulate abnormal spatiotemporal pattern of neuron. Therefore, there is developmental plasticity of visual cortex neuron in the sensitive period, and early treatment is key to superior efficacy.

Alterations in audiovisual simultaneity perception in amblyopia.

Amblyopia is a developmental visual impairment that is increasingly recognized to affect higher-level perceptual and multisensory processes. To further investigate the audiovisual (AV) perceptual impairments associated with this condition, we characterized the temporal interval in which asynchronous auditory and visual stimuli are perceived as simultaneous 50% of the time (i.e., the AV simultaneity window). Adults with unilateral amblyopia (n = 17) and visually normal controls (n = 17) judged the simultaneity of a flash and a click presented with both eyes viewing. The signal onset asynchrony (SOA) varied from 0 ms to 450 ms for auditory-lead and visual-lead conditions. A subset of participants with amblyopia (n = 6) was tested monocularly. Compared to the control group, the auditory-lead side of the AV simultaneity window was widened by 48 ms (36%; p = 0.002), whereas that of the visual-lead side was widened by 86 ms (37%; p = 0.02). The overall mean window width was 500 ms, compared to 366 ms among controls (37% wider; p = 0.002). Among participants with amblyopia, the simultaneity window parameters were unchanged by viewing condition, but subgroup analysis revealed differential effects on the parameters by amblyopia severity, etiology, and foveal suppression status. Possible mechanisms to explain these findings include visual temporal uncertainty, interocular perceptual latency asymmetry, and disruption of normal developmental tuning of sensitivity to audiovisual asynchrony.

Amblyopia: Can Laser Acupuncture be an Option?

This paper describes the results of the treatment of amblyopia in young patients using an unconventional laser-acupuncture technique. After obtaining satisfactory results in the treatment of a 14-year-old amblyopic girl, the treatment was applied to 13 amblyopic children aged 3-11 years, with an encouraging outcome. An ultralow-light-intensity laser with a square-wave modulated emission was applied over a sequence of acupuncture points. Each session lasted < 15 minutes, and the treatment was performed once a week in 6-week cycles. Patients were followed for several years to evaluate the long-term results and/or to extend the treatment. All except two of the treated patients showed a rapid increase in visual acuity after several treatment sessions. Some required retreatment for regressions in visual acuity. The need for medium-term treatment cycles seems, however, to suggest that results may not be stable for all individuals. Although acupuncture has already been proved to be effective in the treatment of amblyopia, the results reported in this paper suggest that laser acupuncture at ultra-low-light-intensity levels can provide similar, if not better, results to conventional acupuncture stimulation, but with higher patient compliance.

[Treatment of Unilateral Amblyopia. Comparison of Methods CAM and CRCS Color Reversal Checkerboard Stimulation of Retina]. / Lécba anizometropické amblyopie. Srovnání metod CAM zrakového stimulátoru a BRS barevné reverzacní stimulace sítnice.

The authors evaluate the effectiveness of new method - Color Reversal Checkerboard Stimulation of the retina (CRCS) in the treatment of unilateral anisometropic amblyopia in group of total 157 children followed during the period 2008-2012 at the Department of Pediatric Ophthalmology, University Hospital and Masaryk University in Brno. The authors evaluate the improvement in best corrected visual acuity in groups of children with myopic and hyperopic anisometropia and compare the effectiveness of CRCS with a commonly used pleoptic method Campbell visual stimulator. Authors introduce an original method in the amblyopia treatment suitable to upgrade current methods of pleoptics.

The distinct role of NR2B subunit in the enhancement of visual plasticity in adulthood.

BACKGROUND: Experience-dependent plasticity is confined to the critical period of early postnatal life, and declines dramatically thereafter. This attenuation promotes the stabilization of cortical circuits, but also limits functional recovery of several brain diseases. The cognitive functions and synaptic plasticity in the hippocampus and prefrontal cortex are elevated following chronic magnesium treatment. Here, we explored the effect of magnesium treatment on visual plasticity and the potential clinical significance. RESULTS: Visual plasticity in adult mice was dramatically enhanced following magnesium treatment, which was concurrent with an increase in the expression of NR2 subunits of N-methyl-D-aspartate receptors. Blockade of NR2B activity in both the induction and expression periods of plasticity prevented this reinstatement. However, the plasticity restored via a decrease in cortical inhibition was independent on the activation of NR2B, indicating a different underlying mechanism. The functional excitatory synapses on layer 2/3 pyramidal neurons were increased following magnesium supplementation. Moreover, the synaptic and neuronal responses were reminiscent of that within the critical period, and this rejuvenation of adult visual cortex facilitated the recovery of visual functions in amblyopia. CONCLUSIONS: Collectively, our data reveal two distinct mechanisms underlying the restoration of visual plasticity in adulthood, and the rejuvenation of adult visual cortex following magnesium treatment provides a new avenue to develop clinical therapies for adult amblyopia, as well as to explore plasticity-based treatment of other brain diseases, such as stroke and aphasia.

Amblyopia and the binocular approach to its therapy.

There is growing evidence that abnormal binocular interactions play a key role in amblyopia. In particular, stronger suppression of the amblyopic eye has been associated with poorer amblyopic eye visual acuity and a new therapy has been described that directly targets binocular function and has been found to improve both monocular and binocular vision in adults and children with amblyopia. Furthermore, non-invasive brain stimulation techniques that alter excitation and inhibition within the visual cortex have been shown to improve vision in the amblyopic eye. The aim of this review is to summarize this previous work and interpret the therapeutic effects of binocular therapy and non-invasive brain stimulation in the context of three potential neural mechanisms; active inhibition of signals from the amblyopic eye, attenuation of information from the amblyopic eye and metaplasticity of synaptic long term potentiation and long term depression.

Audiovisual perception in adults with amblyopia: a study using the McGurk effect.

PURPOSE: The effects on multisensory integration have rarely been examined in amblyopia. The McGurk effect is a well-established audiovisual illusion that is manifested when an auditory phoneme is presented concurrently with an incongruent visual phoneme. Visually healthy viewers will hear a phoneme that does not match the actual auditory stimulus, having been perceptually influenced by the visual phoneme. This study examines audiovisual integration in adults with amblyopia. METHODS: Twenty-two subjects with amblyopia and 25 visually healthy controls participated. Participants viewed videos of combinations of visual and auditory phonemes, and were asked to report what they heard. Some videos had congruent video and audio (control), whereas others had incongruent video and audio (McGurk). The McGurk effect is strongest when the visual phoneme dominates over the audio phoneme, resulting in low auditory accuracy on the task. RESULTS: Adults with amblyopia demonstrated a weaker McGurk effect than visually healthy controls (P = 0.01). The difference was greatest when viewing monocularly with the amblyopic eye, and it was also evident when viewing binocularly or monocularly with the fellow eye. No correlations were found between the strength of the McGurk effect and either visual acuity or stereoacuity in subjects with amblyopia. Subjects with amblyopia and controls showed a similar response pattern to different speakers and syllables, and subjects with amblyopia consistently demonstrated a weaker effect than controls. CONCLUSIONS: Abnormal visual experience early in life can have negative consequences for audiovisual integration that persists into adulthood in people with amblyopia.

How the mechanisms of long-term synaptic potentiation and depression serve experience-dependent plasticity in primary visual cortex.

Donald Hebb chose visual learning in primary visual cortex (V1) of the rodent to exemplify his theories of how the brain stores information through long-lasting homosynaptic plasticity. Here, we revisit V1 to consider roles for bidirectional 'Hebbian' plasticity in the modification of vision through experience. First, we discuss the consequences of monocular deprivation (MD) in the mouse, which have been studied by many laboratories over many years, and the evidence that synaptic depression of excitatory input from the thalamus is a primary contributor to the loss of visual cortical responsiveness to stimuli viewed through the deprived eye. Second, we describe a less studied, but no less interesting form of plasticity in the visual cortex known as stimulus-selective response potentiation (SRP). SRP results in increases in the response of V1 to a visual stimulus through repeated viewing and bears all the hallmarks of perceptual learning. We describe evidence implicating an important role for potentiation of thalamo-cortical synapses in SRP. In addition, we present new data indicating that there are some features of this form of plasticity that cannot be fully accounted for by such feed-forward Hebbian plasticity, suggesting contributions from intra-cortical circuit components.

[Effect of acupuncture on pattern-visual evoked potential in rats with monocular visual deprivation].

OBJECTIVE: To explore electrophysiology mechanism of acupuncture for treatment and prevention of visual deprivation effect. METHODS: Eighteen healthy 15-day Evans rats were randomly divided into a normal group, a model group and an acupuncture group, 6 rats in each one. Deprivation amblyopia model was established by monocular eyelid suture in the model group and acupuncture group. Acupuncture was applied at "Jingming" (BL 1), "Chengqi" (ST 1), "Qiuhou" (EX-HN 7) and "Cuanzhu" (BL 2) in the acupuncture group. The bilateral acupoints were selected alternately, one side for a day, and totally 14 days were required. The effect of acupuncture on visual evoked potential in different spatial frequencies was observed. METHODS: Under three different kinds of spatial frequencies of 2 X 2, 4 X 4 and 8 X 8, compared with normal group, there was obvious visual deprivation effect in the model group where P1 peak latency was delayed (P<0.01) while N1 -P1 amplitude value was decreased (P<0.01). Compared with model group, P1 peak latency was obviously ahead of time (P<0.01) while N1-P1 amplitude value was increased (P<0.01) in the acupuncture group, there was no statistical significance compared with normal group (P>0.05). Under spatial frequency of 4 X 4, N1-P1 amplitude value was maximum in the normal group and acupuncture group. With this spatial frequency the rat's eye had best resolving ability, indicating it could be the best spatial frequency for rat visual system. CONCLUSION: The visual system has obvious electrophysiology plasticity in sensitive period. Acupuncture treatment could adjust visual deprivation-induced suppression and slow of visual response in order to antagonism deprivation effect.

Transcranial direct current stimulation enhances recovery of stereopsis in adults with amblyopia.

Amblyopia is a neurodevelopmental disorder of vision caused by abnormal visual experience during early childhood that is often considered to be untreatable in adulthood. Recently, it has been shown that a novel dichoptic videogame-based treatment for amblyopia can improve visual function in adult patients, at least in part, by reducing inhibition of inputs from the amblyopic eye to the visual cortex. Non-invasive anodal transcranial direct current stimulation has been shown to reduce the activity of inhibitory cortical interneurons when applied to the primary motor or visual cortex. In this double-blind, sham-controlled cross-over study we tested the hypothesis that anodal transcranial direct current stimulation of the visual cortex would enhance the therapeutic effects of dichoptic videogame-based treatment. A homogeneous group of 16 young adults (mean age 22.1 ± 1.1 years) with amblyopia were studied to compare the effect of dichoptic treatment alone and dichoptic treatment combined with visual cortex direct current stimulation on measures of binocular (stereopsis) and monocular (visual acuity) visual function. The combined treatment led to greater improvements in stereoacuity than dichoptic treatment alone, indicating that direct current stimulation of the visual cortex boosts the efficacy of dichoptic videogame-based treatment. This intervention warrants further evaluation as a novel therapeutic approach for adults with amblyopia.

Visual outcome in isoametropic amblyopic children with high hyperopia and the effect of therapy on retinal thickness.

PURPOSE: To assess correlations between associated factors and treatment outcome of isoametropic amblyopia attributable to high hyperopia in children and to evaluate changes in retinal thickness during amblyopic treatment. DESIGN: Retrospective (visual outcome) and prospective (retinal thickness) study. METHODS: Isoametropic (spherical equivalent ≥5.00 diopters in both eyes) amblyopic subjects (n = 217) with corrected visual acuity (VA) ≤0.5 (20/40) for children <5 years old and VA ≤0.6 (20/32) for children 6-10 years old were included. Sixty-nine of these children had refractive accommodative esotropia. All subjects were treated by full-time wearing of optical correction. The magnitude of spherical equivalent hyperopia, age at first treatment, VA, treatment duration, and binocular alignment were analyzed. Thicknesses of the retinal macula and nerve fiber layer were measured using optical coherence tomography in selected amblyopic children (n = 27) during treatment and in control subjects (n = 31). RESULTS: The mean follow-up was 28.8 months. The age at first optical correction ranged from 3 to 10 years. The mean VA improved from 0.38 to 0.82, with 74.7% having acuity ≥0.8 and 28.6% having acuity ≥1.0. VA improvement was positively correlated with duration of treatment and negatively correlated with age at first correction. Foveal thickness slightly decreased after treatment; however, it was not correlated with visual improvement. CONCLUSION: Visual acuity of isoametropic amblyopia improved satisfactorily with spectacle correction and vision therapy. Treatment duration had the greatest impact on VA improvement. Age at first correction also influenced VA improvement but was not a good clinical predictor. Foveal thinning occurring with treatment was not correlated with visual improvement.